In my experience, birding in thick brush is basically impossible without fill light. Getting the HSS right matters cuz you'll miss the action if your gear lags. Just watch the weather sealing tho. Honestly, i've been super happy with these: * Godox V1-C Round Head Flash for Canon - amazing catchlights
* Godox V860III-C TTL Li-Ion Flash for Canon - fast recycle ngl, they handle HSS perfectly on the 90D. gl!

Honestly, shooting birds with AA batteries is basically a total nightmare. I had issues with recycle lag on the old Canon units, which was sooo disappointing. For ur 90D, skip the V1 and grab the Godox V860III-C TTL Li-Ion Flash for Canon. Its Li-ion battery is literally a game changer for speed. Pair it with a MagMod MagBeam Wildlife Kit to get that perfect catchlight at a distance without draining your power. GL!

Adding my two cents here! Honestly, I get being worried about the price of the Canon gear... it is literally insane. But if you’re shooting in dense foliage, you gotta be careful with weather sealing. Most third-party stuff says it’s "weather resistant" but I wouldnt trust it in a heavy downpour, you know? Like, be careful cuz moisture can fry the electronics pretty fast if you aren't using a rain cover. For your 90D, I would suggest looking at these two options that are way more budget-friendly: 1. Godox TT685II-C TTL Flash for Canon
- Pros: Super cheap and the HSS is actually really reliable for those fast shutter speeds you need for birds. - Cons: It uses 4 AA batteries. If you go this route, make sure to get high-quality rechargeables or the recycle time will basically kill your workflow. Also, the build feels a bit plastic-y compared to the pro Canon units. 2. Yongnuo YN600EX-RT II Wireless Speedlite for Canon
- Pros: It’s basically a clone of the Canon one you mentioned, so the UI is very familiar. It handles that natural catchlight in the eyes really well without overexposing everything.
- Cons: Quality control can be a bit "meh" sometimes... ive heard stories of them failing after heavy use. I mean, it’s 1/3 the price, so there’s a trade-off. One tip: I’d maybe look into a Better Beamer Flash Extender FX-3 for Canon too. It concentrates the beam so you dont have to blast the flash at full power. That helps with the recycle lag and might stop you from spooking the wildlife as much. Just make sure the flash is seated tight on the 90D shoe!! Good luck.

Like someone mentioned, you really gotta watch the moisture when you are out in the thick of it. I remember being out at sunrise in this super misty valley last spring... had to wrap my flash in a produce bag from the grocery store. It looked ridiculous but it saved my shoot! I am really satisfied with my Godox TT685II-C TTL Flash for Canon though. It handles the HSS on my 90D perfectly fine and did not cost a fortune.

• Definitely get Panasonic Eneloop Pro AA Rechargeable Batteries for it. I find they give me almost the same recycle speed as the built-in packs for way less money than buying a spare lithium battery.
• I actually made my own bounce card out of a white yogurt lid to get those catchlights. It looks DIY but the light is so soft and natural in the eyes... basically free.
• For the weather thing, I just keep a small roll of electrical tape in my bag to seal up the battery door if it gets really humid. Works well and keeps things dry enough...

So I'm pretty new to all this gear stuff but I've been digging into the spec sheets lately and I totally agree about the price gap. Like, when you look at the market, the first-party Canon gear costs so much more mainly for that guaranteed weather sealing and the autofocus assist beam compatibility. The third-party brands are basically catching up on technical speed, but their documentation on environmental protection is always a bit vague which is realy confusing. Before digging deeper into the brands, I have a couple questions:
1. Are you mostly doing long-distance birding or is the macro stuff more of a priority for you right now?
2. Tbh, what's your actual tolerance for weight? Like, do you need a compact setup or are you okay with a bulky unit on top of your 90D? I'm trying to figure out if the higher GN (Guide Number) specs are even worth it for your specific setup!

So I have been doing the DIY thing with my 90D for a while now and honestly you really need to be careful with how you handle any flash in the field. Even if you get a decent third-party one, the weather sealing is rarely as good as they claim so I always suggest taking some self-service steps to protect your gear.

• Bring some small plastic bags and rubber bands to create a makeshift rain guard for the flash head and the hot shoe area.
• Be super careful with the HSS settings during long birding sessions because that constant high power can actually overheat the tube and cause it to crack if you dont give it breaks.
• Always carry a small micro-fiber cloth to wipe down the flash foot after you come in from the humidity or you will get corrosion on the pins. I have seen way too many people fry their electronics trying to get that one perfect shot in a damp forest lol. Just basically assume the flash is not waterproof and act accordingly or you are gonna have a bad time.